(a) Field of the Invention
The present invention relates to a magnetic bearing structure and a turbo machine having the same, and it particularly relates to a magnetic bearing structure for using a permanent magnet and an electromagnet in a magnetic bearing provided on a side of a rotation body to allow the electromagnet to control a position of the rotation body and allow the permanent magnet to generate a bias magnetic field, and then control a magnetized direction of the permanent magnet to correspond to a shaft direction of a rotation shaft thereby facilitating magnetization, and a turbo machine having the same.
(b) Description of the Related Art
A magnetic bearing device has been widely used for various kinds of precision machine devices. The magnetic bearing device levitates a rotation body and supports it according to a magnetic force generated by an electromagnet. With devices using a magnetic bearing, a shaft does not contact the bearing so dust caused by abrasion is suppressed, a lubricant is not used, and noise is reduced.
A general rigid body has six degrees of freedom (DOF). However, a conventional rotation body rotates the shaft so five DOF excluding a rotation movement of the rotation shaft must be controlled. Therefore, the magnetic bearing applicable to a 5-shaft control device for controlling the entire five DOF is classified as a radial magnetic bearing and an axial magnetic bearing.
Regarding the magnetic bearing, conductor surfaces facing each other pull the rotation body and increase or reduce a magnetic force depending on a position change of the rotation body to stably support the rotation body. However, in this instance, a predetermined bias magnetic force must be applied to the rotation body according to a load caused by the rotation body. To form the bias magnetic force, a permanent magnet is used as well as an electromagnet. Here, to divide paths of magnetic fields of the electromagnet and the permanent magnet, a magnetic bearing structure for using a method for providing a donut-shaped permanent magnet between a pair of electromagnets has been proposed.
In the case of the above-structured magnetic bearing, the magnetized direction of the donut-shaped permanent magnet must be perpendicular to the shaft direction of the rotation body, that is, the permanent magnet must be magnetized in a radius direction of the permanent magnet. However, the magnetization method is difficult and production efficiency of the magnetic bearings can be worsened. Therefore, it is required to provide a magnetic bearing structure for easily magnetizing the permanent magnet while dividing the magnetic field paths of the permanent magnet and the electromagnet.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.